A number of different techniques have been employed to use wireless media or wireless resources more efficiently. For example, it is common for wireless nodes or devices to provide rate adaptation, where a modulation scheme may be adjusted based on changing channel conditions. This may allow higher order modulation schemes to be used where channel conditions are more favorable.
For example, as described in “WCDMA for UMTS—Radio Access For Third Generation Mobile Communications”, H. Holma and A. Toskala (editors), 2005, wireless technologies such as Wideband Code-Division Multiple Access (WCDMA) through high-speed downlink packet access (HSDPA) and Third Generation Partnership Project (3GPP) UTRAN Long Term Evolution may allow improved exploitation of radio channel variations through link adaptation and channel dependent scheduling. Data transmission rate may be adjusted based on downlink channel quality information (CQI) provided as feedback from the wireless node (or user terminal, UE) to the scheduler located in the infrastructure node (or base station, eNodeB).
In addition to adaptation in the time-domain as exemplified in e.g. HSDPA, wireless systems based on orthogonal frequency domain multiple access (OFDMA), such as the UTRAN Long Term Evolution “Technical Solution for the 3G Long-Term Evolution,” Ekstrom, et al, March, 2006 allow for channel dependent scheduling also in the frequency domain provided that information about the channel quality in both time and frequency at each UE (user equipment) location are available at the scheduling node.
In addition, there are different techniques that have been developed to report or provide channel quality information (CQI) (or channel quality indication), to a packet scheduler for OFDMA systems. For example, the best-M method allows a wireless node to report channel quality information for the M highest quality channels (or sub-channels). As another example, a threshold CQI technique may be employed, where a wireless node may report channel quality information for the best or highest quality channel, and for other channels having a channel quality that is within a specific threshold of the best or highest quality channel. Unfortunately, current techniques for feedback and link adaptation may not sufficiently adapt to changing channel conditions or network complexities.